1 /* $NetBSD: term_chk.c,v 1.8 2009/04/14 07:59:17 lukem Exp $ */ 2 3 /* 4 * Copyright (c) 1989, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/cdefs.h> 36 #ifndef lint 37 __RCSID("$NetBSD: term_chk.c,v 1.8 2009/04/14 07:59:17 lukem Exp $"); 38 #endif 39 40 #include <sys/types.h> 41 #include <sys/param.h> 42 #include <sys/stat.h> 43 #include <time.h> 44 #include <stdio.h> 45 #include <errno.h> 46 #include <unistd.h> 47 #include <paths.h> 48 #include <fcntl.h> 49 #include <string.h> 50 #include <err.h> 51 52 #include "term_chk.h" 53 54 /* 55 * term_chk - check that a terminal exists, and get the message bit 56 * and the access time 57 */ 58 int 59 term_chk(uid_t uid, const char *tty, int *msgsokP, time_t *atimeP, int ismytty, 60 gid_t saved_egid) 61 { 62 char path[MAXPATHLEN]; 63 struct stat s; 64 int i, fd, serrno; 65 66 if (strstr(tty, "../") != NULL) { 67 errno = EINVAL; 68 return -1; 69 } 70 i = snprintf(path, sizeof path, _PATH_DEV "%s", tty); 71 if (i < 0 || i >= (int)sizeof(path)) { 72 errno = ENOMEM; 73 return -1; 74 } 75 76 (void)setegid(saved_egid); 77 fd = open(path, O_WRONLY, 0); 78 serrno = errno; 79 (void)setegid(getgid()); 80 errno = serrno; 81 82 if (fd == -1) 83 return(-1); 84 if (fstat(fd, &s) == -1) 85 goto error; 86 if (!isatty(fd)) 87 goto error; 88 if (s.st_uid != uid && uid != 0) { 89 errno = EPERM; 90 goto error; 91 } 92 if (msgsokP) 93 *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */ 94 if (atimeP) 95 *atimeP = s.st_atime; 96 if (ismytty) 97 (void)close(fd); 98 return ismytty ? 0 : fd; 99 error: 100 if (fd != -1) { 101 serrno = errno; 102 (void)close(fd); 103 errno = serrno; 104 } 105 return -1; 106 } 107 108 char * 109 check_sender(time_t *atime, uid_t myuid, gid_t saved_egid) 110 { 111 int myttyfd; 112 int msgsok; 113 char *mytty; 114 115 /* check that sender has write enabled */ 116 if (isatty(fileno(stdin))) 117 myttyfd = fileno(stdin); 118 else if (isatty(fileno(stdout))) 119 myttyfd = fileno(stdout); 120 else if (isatty(fileno(stderr))) 121 myttyfd = fileno(stderr); 122 else if (atime == NULL) 123 return NULL; 124 else 125 errx(1, "Cannot find your tty"); 126 if ((mytty = ttyname(myttyfd)) == NULL) 127 err(1, "Cannot find the name of your tty"); 128 if (strncmp(mytty, _PATH_DEV, sizeof(_PATH_DEV) - 1) == 0) 129 mytty += sizeof(_PATH_DEV) - 1; 130 if (term_chk(myuid, mytty, &msgsok, atime, 1, saved_egid) == -1) 131 err(1, "%s%s", _PATH_DEV, mytty); 132 if (!msgsok) { 133 warnx( 134 "You have write permission turned off; no reply possible"); 135 } 136 return mytty; 137 } 138